1. Field of the Invention
The present invention relates to a semiconductor device inspection system used, for example, in anomaly occurrence analysis or reliability evaluation of semiconductor devices. More particularly, the invention relates to a semiconductor device inspection system for detecting from the bottom surface side very weak light in the infrared region as emitted from an anomalous portion in a semiconductor device.
2. Related Background Art
With an increase in integration of semiconductor devices, internal circuits tend to become finer and more complicated, which results in making difficult the detailed anomaly occurrence analysis or reliability evaluation of internal circuits.
In such an existing state, much attention is focused on the analysis technology to track down the location of an anomalous portion by detecting very weak light emitted from the anomalous portion in semiconductor device. An emission microscope is known as a semiconductor device inspection apparatus utilizing such analysis technology.
The emission microscope picks up with high sensitivity very weak light as caused by hot carriers, which are produced when an electric field is concentrated on an anomalous portion in a semiconductor device, or very weak light in the infrared region as caused by recombination, for example in latchup. Therefore, the emission microscope has an excellent function to inspect a semiconductor device to be checked with no contact and with high accuracy while being superior in operability.
The emission microscope, however, has the following problem. Since it detects emission in the visible to infrared region, it could become incapable of measuring emission if there exists some shielding object between an anomalous portion emitting very weak light and the emission microscope.
Specifically, highly integrated devices such as VLSI semiconductor devices tend to employ the chip structure in which interconnection between numerous elements such as transistors is made by multilayer wiring located on the top surface side. The multilayer wiring is likely to interrupt the very weak light caused by an anomaly of an element underneath the multilayer wiring, thus causing a problem of inability to measure or not permitting high-accuracy measurement. Also, a semiconductor device to which the packaging structure is applied has such an arrangement that a lead frame covers the top of the semiconductor chip. Thus, similar to the case of the multilayer wiring, the lead frame will act as a shielding object to interrupt the very weak light, resulting in inability of measurement or not permitting high-accuracy measurement.
Further, there is another problem in applications of the emission microscope. In the case of observation of an anomalous portion in a plastic-molded semiconductor device, the top plastic mold layer is chemically removed for example by fuming nitric acid to expose the surface of the semiconductor chip. Further, a predetermined bias power source is connected to a lead frame to supply power to internal circuits formed in the semiconductor chip. With the power supply, very weak light is emitted from an anomalous portion, which is observed from the top side of the semiconductor chip. When the plastic mold is chemically removed for example by fuming nitric acid, the internal circuits or other elements formed in the semiconductor chip could be damaged, which could interfere with observation of an anomalous portion.